Forming die for contact lens and contact lens manufacturing method using the forming die

ABSTRACT

A forming die for a contact lens, wherein flat mutual contact areas ( 62 ) allowed to abut on each other on the outer peripheral side of a contact lens forming cavity ( 15 ) are formed to have a width of 0.01 mm or wider under the condition that a female die ( 12 ) mates a male die ( 14 ), a generally closed auxiliary cavity ( 64 ) filled with a polymerization monomer ( 66 ) is formed on the outer peripheral side of the mutual contact areas ( 62 ), and a tubular fitted part ( 60 ) allowing both the female and male dies ( 12 ) and ( 14 ) to be fitted to each other by tubular surfaces ( 30 ) and ( 50 ) extending in the die mating direction is formed on the outer peripheral side of the auxiliary cavity ( 64 ), whereby the forming cavity can be stably formed in the closed state by mating both the male and female dies each other so that the contact lens can be accurately and stably molded while preventing defective molding such as burrs.

TECHNICAL FIELD

The present invention relates to a contact lens forming die formanufacturing contact lenses by a molding process, and to a contact lensmanufacturing method employing it. More particularly, the presentinvention relates to a contact lens forming die, whereby closure can bestably provided to the lens edge portion in the forming cavity, andwhereby it possible to consistently obtain mating fixation force of themale and female forming dies, so as to stably carry out molding of thedesired contact lens. Also, the present invention relates to a contactlens manufacturing method employing the forming die.

BACKGROUND ART

The molding process is one type of manufacturing method that has beenused to date for both hard contact lenses and soft contact lenses. Themolding process as taught, for example, in Patent Citation 1 or PatentCitation 2, involves mating a female die having a concave forming facewith a male die having a convex forming face to produce a contact lensforming cavity between the mated faces of the male and female dies, andinjecting a predetermined polymerizable monomer as a lens formingmaterial into the cavity that is subjected to polymerization within thedie cavity, to manufacture a contact lens of a shape corresponding tothat of the forming cavity. As compared to other known contact lensmanufacturing methods, such as the lens cutting method(cutting/polishing method) or spin casting method (centrifugal castingmethod), it is possible to mass-produce the desired contact lens atlower cost. Thus, the process has been studied for possible applicationin production of disposable contact lenses and the like.

With the molding process, the mating faces of the male and female diesare situated at the peripheral edge portion of the lens. Thus, in orderto reduce or avoid burrs and other molding defects of the molded contactlens, it is important that the peripheral portion of the forming thatcorresponds to the lens edge portion be able to stably maintain a closedstate. Typically, after the male and female dies have been mated and apolymerizable material supplied to them, the assembly is conveyed to apolymerization processing device where it is processed by irradiationwith ultraviolet, heating, or the like. Thus, in order to stably carryout the forming process after die mating, it is desirable for the maleand female dies to be held securely in the mated state. Accordingly,Patent Citation 3, Patent Citation 4, and Patent Citation 5, forexample, propose a die structure whereby at the peripheral edge portionof the forming cavity, an annular edge portion formed on either the maleor female die is brought into abutment with the other die in the axialdirection, in order to direct intensive localized action of the dieclosing force to the peripheral edge portion of the forming cavity andimprove sealing of the forming cavity. Patent Citation 6 proposes a diestructure whereby a thin annular rim projection formed on either themale or female die at the peripheral edge portion of the forming cavityis brought into abutment with the other die in the axial direction,whereby upon mating the dies, the annular rim projection undergoesdeformation following the profile of the other die, improving sealing ofthe forming cavity.

The former forming die provided with the edge portion taught in PatentCitations 3-5 has the drawback that since the peripheral portion of theforming cavity only comes into abutment over a miniscule zone at thedistal edge of the edge portion, it is difficult to provide stableclosure at the peripheral portion of the forming cavity, and that evenslight relative tilting of the male and female dies can result in a gapforming between the annular edge portion and the abutting face. Thisresults in the risk of burrs or other molding defects occurring at theperipheral edge of the contact lens molding. In the latter forming dieprovided with the annular rim projection taught in Patent Citation 6,since it is difficult to form such a thin annular rim projection on theforming die, there is the problem that manufacture of the forming dieper se is complicated and expensive. Additionally, since the annular rimprojection is thin and easily deformable, it is difficult for it toassume a consistent shape during abutment, and there is risk that due toslight relative tilting of the male and female dies, the distal edge ofthe annular rim projection may jut out into the interior of the formingcavity, making it difficult to achieve adequate molding stability.

(Patent Citation 1)

JP-A-50-151966

(Patent Citation 2)

JP-A-55-151618

(Patent Citation 3)

JP-A-2-172712

(Patent Citation 4)

JP-A-6-208090

(Patent Citation 5)

JP-A-2000-289041

(Patent Citation 6)

JP-A-1-500256

DISCLOSURE OF THE INVENTION

With the foregoing in view, it is an object of the present invention toprovide a contact lens forming die of novel construction whereby theforming cavity can be stably provided closure during mating, and wherebyit possible to consistently obtain mating fixation force of the male andfemale forming dies, so as to be able to stably carry out molding of thedesired contact lens; as well as a contact lens manufacturing methodemploying the same.

Modes of the invention for solving the aforementioned problems aredescribed hereinbelow. Constituent elements employed in the modes setforth hereinbelow may be combined in any of various possible ways. Themodes and technical features of the invention are not limited to thosedisclosed hereinbelow, and should be appreciated on the basis of theinventive concept disclosed in the description as a whole and theaccompanying drawings, or that would be apparent to the practitioner ofthe art from these disclosures.

FIRST MODE OF THE INVENTION

The invention in a first mode thereof is a contact lens forming diecomprising a female die having a concave forming face and a male diehaving a convex forming face, which are mated with each other to createa forming cavity between the opposed concave forming face and convexforming face, the forming cavity adapted to be filled with polymerizablemonomer which is polymerized to form a contact lens, characterized inthat by means of mating the female die and the male die with each other,annular flat mutual contact areas extending over a width of 0.01 mm orgreater in a direction orthogonal to a die mating direction are formedby abutting the female and male dies at an outer peripheral side of theconcave forming face and the convex forming face; and at an outerperipheral side of the mutual contact areas an auxiliary cavity ofsubstantially closed structure to be filled with the polymerizablemonomer during molding is formed by the female and male dies positionedspaced apart in opposition to each other in the die mating direction;while a tubular fitted part is formed by fitting together of the femaleand male dies at an outer peripheral side of the auxiliary cavity bymeans of tubular surfaces extending in the die mating direction.

In the contact lens forming die of construction according to this mode,the forming cavity situated on the inner peripheral side and theauxiliary cavity situated on the outer peripheral side are formed toeither side of the mutual contact areas of the male and female diesmating the peripheral edge of the forming cavity with the dies in themated state. The forming cavity and the auxiliary cavity are then filledwith polymerizable monomer, and the polymerizable monomer within the twocavities is subjected to a polymerization process, whereby force exertedon the male and female dies due to polymerization shrinkage of thepolymerizable monomer filling the cavities is exerted on the male andfemale molds in the die mating direction, in the forming cavity portionsituated to the inner peripheral side of the mutual contact areas andthe auxiliary cavity portion situated to the peripheral of the mutualcontact areas, respectively.

Thus, by means of force created by polymerization shrinkage of thepolymerizable monomer exerted respectively on the forming cavity and theauxiliary cavity, acting force in the die mating direction is exerted toboth the inner peripheral side and the outer peripheral side of themutual contact areas. Thus, the resultant force of the acting force onthe inner peripheral side and outer peripheral side of the mutualcontact areas is attracted as a pushing force on the mutual contactareas in the direction of abutment of the male and female dies in themating direction. In conjunction with the annular extending flat shapeof predetermined width dimension of 0.01 mm or greater of these mutualcontact areas, the male and female dies may be brought into stableabutment at the mutual contact areas thereof in the die matingdirection, whereby the desired forming cavity may be formed with ahighly closed state and good shape stability of the peripheral edgeportion.

Additionally, in the contact lens forming die of construction accordingto this mode, since male and female dies are positioned relatively inthe direction orthogonal to the die mating direction by means of thetubular fitted portion, during mating, the male and female dies can bepositioned easily and highly accurately in the direction orthogonal tothe die mating direction. Thus, at the mutual contact areas as well, themale and female dies can be positioned highly accurately in thedirection orthogonal to the die mating direction, so that shapestability of the peripheral edge portion of the forming cavity duringdie mating can be improved further.

SECOND MODE OF THE INVENTION

The invention in a second mode thereof is a contact lens forming dieaccording to the first mode wherein a capacity of the auxiliary cavityis 1-40% of a capacity of the forming cavity. In this mode, forceexerted on the male and female dies in the die mating direction based onpolymerization shrinkage of the polymerizable monomer filling theauxiliary cavity can be exerted more effectively, and abutment of themale and female dies at the mutual contact areas can be made more secureand stable. However, if the auxiliary cavity is less than 1%, it becomesdifficult to achieve an adequate level of force exerted on the male andfemale dies in the die mating direction based on polymerizationshrinkage of the polymerizable monomer filling the auxiliary cavity,whereas if the auxiliary cavity exceeds 250%, it is possible that wasteof polymerizable monomer filling the auxiliary cavity will become aproblem.

THIRD MODE OF THE INVENTION

The invention in a third mode thereof is a contact lens forming dieaccording to the first or second mode wherein by means of mating thefemale die and the male die with each other, the male and female diesare positioned spaced apart from each other by an outer peripheral sideof the tubular fitted portion, forming an annular monomer reservoir thatcontains an excess polymerizable monomer during molding. In this mode,injection of polymerizable material into the auxiliary cavity during diemating may be carried out stably, while preventing overflow of thepolymerizable monomer to the die exterior.

FOURTH MODE OF THE INVENTION

The invention in a fourth mode thereof is a contact lens forming dieaccording to any one of the first to third modes, wherein in the femaledie, a face forming the auxiliary cavity is a smooth surface devoid ofbumps in an entirety thereof. In this mode, when the male die is alignedwith the female die and the forming cavity and auxiliary cavity arefilled with polymerizable monomer, air expelled from the forming cavityand expelled from the auxiliary cavity flows smoothly, preventing airfrom remaining in the forming cavity or auxiliary cavity. Thus, it ispossible to avoid a situation where air remaining in the auxiliarycavity causes a drop in force in the die mating direction exerted on themale and female dies utilizing polymerization shrinkage, and to achievemore stable force in the die mating direction utilizing polymerizationshrinkage.

FIFTH MODE OF THE INVENTION

The invention in a fifth mode thereof is a contact lens forming dieaccording to any one of the first to fourth modes, wherein the femaledie is formed with an annular flat surface extending in a directiongenerally orthogonal to the die mating direction towards an outerperipheral side from an peripheral edge portion of the concave formingface, the annular flat surface of the female die being brought intoabutment at an inner peripheral portion thereof with the male die so asto form the mutual contact areas, and being positioned at an outerperipheral portion thereof in opposition to the male die spaced aparttherefrom in the die mating direction so as to form the auxiliarycavity. In this mode, zones for formation of the mutual contact areasand the auxiliary cavity in the female die can be formed easily and withhigh accuracy.

SIXTH MODE OF THE INVENTION

The invention in a fifth mode thereof is a contact lens forming dieaccording to the fifth mode, wherein the male die is formed with anannular flat surface extending in a direction generally orthogonal tothe die mating direction towards an outer peripheral side from anperipheral edge portion of the convex forming face, the annular flatsurface of the male diem being brought into abutment with the annularflat surface of the female die so as to form the mutual contact areas,and a sloping face that extends towards the outer peripheral side froman peripheral edge portion of the annular flat surface of the male dieand that moving towards the outer peripheral side becomes graduallyfurther apart in the die mating direction from the annular flat surfaceof the female die, the sloping face being positioned in opposition tothe annular flat surface of the female die so as to form the auxiliarycavity, and having a tapered face that slopes at a predetermined anglein the die mating direction and extends linearly towards the outerperipheral side, or a bowed convex face that projects out to theauxiliary cavity side and extends towards the outer peripheral side. Inthis mode, a forming mold for manufacturing the male die can be easilyprovided by means of a cutting process with the mutual contact area andauxiliary cavity formation zones, making it possible to form formationzones for the mutual contact areas and auxiliary cavity on the male dieeasily and with a high degree of accuracy.

In this mode, during formation of the sloping face of the male die withthe aforementioned bowed convex face, preferably, there will be employeda structure wherein the inner edge side of the bowed convex face and theperipheral edge side of the annular flat surface interconnect smoothlyby a common tangent. By employing this specific bowed convex shape forthe axial sectional shape of the sloping face of the male die, there isafforded smooth flow of polymerizable monomer that when the male andfemale dies are mated fills the forming cavity as well as being squeezedout therefrom to fill the auxiliary cavity, effectively preventing airfrom remaining in the auxiliary cavity. In the initial stage ofpolymerization, there is reduced or eliminated negative pressureassociated with polymerization shrinkage of the polymerizable monomer inthe forming cavity through smooth supply from the auxiliary cavity ofpolymerizable monomer that has not yet polymerized in the auxiliarycavity, effectively avoiding the molding problems such as residualstress or surface sink in the target contact lens. Additionally, sincethe inner edge side of the forming face of the auxiliary cavity in themale mold is formed so as to extend out smoothly from the annular flatportion without any inflection point, a closed state of the formingcavity may be stably achieved by means of mating of the male and femaledies at the annular flat portions. This makes it possible to moreconsistently achieve the desired edge shape in the contact lens. Also,since a shape that smoothly interconnects the annular flat portion andthe auxiliary cavity forming face can be readily imparted by a singlecontinuous forming face by means of a single mold member in the moldused to form the male die, the occurrence of burrs or the like at theinterface of the annular flat portion and the auxiliary cavity formingface can be readily prevented, so that a closed state of the formingcavity with mating of the male and female dies at the annular flatportions can be more stably achieved.

SEVENTH MODE OF THE INVENTION

The invention in a seventh mode thereof is a contact lens forming dieaccording to any one of the first to sixth modes, wherein the tubularsurface making up the tubular fitting portion in the female die isformed projecting from a peripheral edge side of an auxiliary cavityforming face in the die mating direction of the female die with the maledie. In this mode, with the concave forming face of the female diesupported open upward in the vertical direction, the male die can bemated onto the female die from above, whereby for example, by injectinga predetermined quantity of polymerizable monomer onto the concaveforming face of the female die prior to mating, it is possible toefficiently and stably fill the forming cavity with polymerizablemonomer by means of mating the male and female dies.

EIGHTH MODE OF THE INVENTION

The invention in an eighth mode thereof is a contact lens forming diepertaining to any of the first to seventh modes wherein a gap forexpelling excess polymerizable monomer in the auxiliary cavity to anoutside during mating of the male and female dies is formed in thetubular fitting portion. In this mode, even in the event that the maleand female dies are not mated at high pressure, it is neverthelesspossible to reduce or avoid a rise in filling pressure of thepolymerizable monomer in the forming cavity, making it possible to formthe lens with greater precision, as well as avoiding an initial highpressure state in the auxiliary cavity so that it is possible to moreeffectively achieve the desired mating assist force on the male andfemale dies brought about in association with polymerization shrinkageof the polymerizable monomer.

NINTH MODE OF THE INVENTION

The invention in a ninth mode thereof relates to a method formanufacturing a contact lens using the contact lens forming dieaccording to any one of the first to eighth modes, characterized in thatwith the forming cavity and the auxiliary cavity formed between themating faces of the female die and the male die being filled with thepolymerizable monomer, the polymerizable monomer filling the formingcavity and the auxiliary cavity is subjected to a polymerizationprocess. According to the manufacturing method of this mode, force inthe mating direction exerted on the male and female dies on the basis ofpolymerization shrinkage of the polymerizable monomer filling theforming cavity, and force exerted on the male and female dies on thebasis of polymerization shrinkage of the polymerizable monomer fillingthe auxiliary cavity, are exerted at generally the same time on theinner peripheral side and outer peripheral side to either side of themutual contact areas. Therefore, the action of an unbalanced load on themutual contact areas is prevented, and the male and female dies arestably and securely abutted at the mutual contact areas, therebyeffectively preventing the occurrence of burrs or other defects in thelens edge portion of the contact lens, so that the desired contact lenscan be molded consistently with high accuracy.

TENTH MODE OF THE INVENTION

The invention in a tenth mode thereof is a method for manufacturing acontact lens according to the ninth mode, wherein the mating directionof the male and female dies is generally vertical, with the male diebeing mated relative to the female die from above in the verticaldirection. In this mode, prior to mating, by injecting a predeterminedquantity of polymerizable monomer onto the concave forming face of thefemale die, it is possible to efficiently and stably fill the formingcavity with polymerizable monomer by means of mating the male and femaledies.

ELEVENTH MODE OF THE INVENTION

The invention in an eleventh mode thereof is a method for manufacturinga contact lens according to the eighth or tenth mode, wherein at leastone die selected from the male die and the female die is a forming dieof synthetic resin, and with the male and/or female die of syntheticresin in a softened state at high temperature, the polymerizable monomeris supplied between the opposed face of the male and female dies, whilemating the male and female dies so that the forming cavity and theauxiliary cavity are filled with the polymerizable monomer. In thismode, when mating the male and female dies so that they abut at themutual contact areas, the abutting faces of the male and female diesundergo deformation so as to conform to each other, whereby the abuttingstate at the mutual contact areas can be more advantageously and stablyrealized.

Thus, mold dimension error in the forming mold and the like can becompensated for or eliminated, making it possible to more consistentlycarry out molding of the desired contact lens. As will be apparent fromthis, in this mode, at the time of mating of the male and female dies,at least one die selected from the male die and the female die will bebrought to softened state at high temperature, at least at the portionsthereof forming the mutual contact areas.

TWELFTH MODE OF THE INVENTION

The invention in an twelfth mode thereof is a method for manufacturing acontact lens according to the eleventh mode, wherein at least one dieselected from the male die and the female die is a forming die ofsynthetic resin, with the male and/or female die of synthetic resinbeing mated used in a high temperature state prior to completely coolingafter molding thereof. In this mode, since no special heating means isneeded to bring the forming die into a softened state at hightemperature, and since the problem of deformation or strain due toreheated after cooling the forming die can be avoided, dimensionalaccuracy of the desired contact lens can be improved as well.

EFFECTS OF THE INVENTION

As will be apparent from the preceding description, in the contact lensforming die of construction according to the present invention, duringmating, the male and female dies are positioned with high accuracy on acenter axis by tubular fitter portions, and are stably closed at widemutual contact areas formed to the outer peripheral side of the formingcavity. Additionally, by putting to good use polymerization shrinkage ofthe polymerizable monomer exerted on the forming cavity formed on theinner peripheral side of the mutual contact areas and on the auxiliarycavity formed on the outer peripheral side, abutting force of the maleand female dies in the mutual contact areas can be effectively andstably achieved. Thus, at the mating faces of the male and female dies,it is possible to form the forming cavity with high accuracy andstability, and thus contact lenses of the desired shape can be moldedwith high accuracy and stability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of the contact lens forming dieas an embodiment of the invention, shown in the mated state.

FIG. 2 is a longitudinal sectional view showing an enlargement of arelevant part of the contact lens forming die of FIG. 1.

FIG. 3 is an illustration of a manufacturing process for a contact lensaccording to the method of the invention, using the forming die shown inFIG. 1.

FIG. 4 is an illustration of another manufacturing process for a contactlens according to the method of the invention, using the forming dieshown in FIG. 1.

FIG. 5 is a longitudinal sectional view corresponding to FIG. 2, showingan enlargement of a relevant part of the contact lens forming die asanother embodiment of the invention.

FIG. 6 is a longitudinal sectional view corresponding to FIG. 2, showingan enlargement of a relevant part of the contact lens forming die as yetanother embodiment of the invention.

FIG. 7 is a longitudinal sectional view corresponding to FIG. 2, showingan enlargement of a relevant part of the contact lens forming die as yetanother embodiment of the invention.

FIG. 8 is a longitudinal sectional view corresponding to FIG. 2, showingan enlargement of a relevant part of the contact lens forming die asstill another embodiment of the invention.

FIG. 9 is a sectional view taken along 9-9 in FIG. 8.

FIG. 10 is a longitudinal sectional view corresponding to FIG. 2,showing an enlargement of a relevant part of the contact lens formingdie as still another embodiment of the invention.

FIG. 11 is a sectional view taken along 11-11 in FIG. 10.

FIG. 12 is a longitudinal sectional view corresponding to FIG. 2,showing an enlargement of a relevant part of the contact lens formingdie as still another embodiment of the invention.

FIG. 13 is a sectional view taken along 13-13 in FIG. 12.

FIG. 14 is a longitudinal sectional view corresponding to FIG. 2,showing an enlargement of a relevant part of the contact lens formingdie as yet another embodiment of the invention.

FIG. 15 is a sectional view taken along 15-15 in FIG. 14.

BEST MODE FOR CARRYING OUT THE INVENTION

A more specific understanding of the invention will be provided throughthe following detailed description of the embodiments with reference tothe accompanying drawings.

A contact lens forming die 10 as a first embodiment of the invention isshown in FIG. 1. The forming die 10 is composed of a female die 12 and amale die 14; with the female and male dies 12, 14 mated with each otheras shown in the drawing, a contact lens forming cavity 15 is formedbetween the mating faces of the female and male dies 12, 14.

More specifically, the female die 12 and the male die 14 are formed withshapes, dimensions and materials having rigidity sufficient to maintainconstant shape of the forming cavity 15 during molding. In thisembodiment in particular, the female and male dies 12, 14 are eachformed of thermoplastic resin material. For instance, synthetic resinssuch as polypropylene (PP), polyethylene (PE), polyethyleneterephthalate (PET), polystyrene (PS), polycarbonate (PC), polyvinylchloride (PVA), nylon (PA), polyacetal (POM) and fluororesins aresuitable as forming materials. Between the female die 12 and the maledie 14, the same material may be employed for both dies 12, 14, ordifferent materials may be employed. Besides synthetic resins, otherforming materials for the female die 12 and the male die 14 includethermosetting resins, glass, metal, and various other materials,selected according to the required molding accuracy and moldingconditions employed.

The female die 12, which is formed as a synthetic resin molded productas stated above, has an overall concave shape that opens upward, andgenerally has the shape of a body of rotation about the die center axis16. More specifically, the center portion of the female die 12 isconstituted as a spherical shell 18 that projects downward, with atapered tubular portion 22 that extends upward integrally formed on theouter peripheral side of the spherical shell 18 via a shoulder portion20, and with a flange portion 24 that spreads outwardly in theaxis-perpendicular direction integrally formed on the upper rim of thetapered tubular portion 22.

On the spherical shell 18, there is formed a concave forming face 25that corresponds to the front curve of the target contact lens, thisface being constituted by the surface on the concave side, which is theface opening upward and facing in one axial direction (upward in FIG.1). The shoulder portion 20 extends in the circumferential directionwith a generally “L” shaped cross section that projects slightly outwardin the axis-perpendicular direction of the outer peripheral edge of thespherical shell 18 and then projects deflecting axially upward. As shownin FIG. 2, by means of the shoulder portion 20, there is formed anannular flat portion 26 that spreads outward in the axis-perpendiculardirection from the outer peripheral edge of the concave forming face 25.This annular flat portion 26 connects with the outer peripheral edge ofthe concave forming face 25 by means of an edge portion 28, andconstitutes a flat face of annular shape extending continuously aroundthe entire circumference in the circumferential direction, spreadingoutwardly in the axis-perpendicular direction by a constant widthdimension: B. On the shoulder portion 20 is formed a vertical tubularinner peripheral surface 30 that rises at an approximate right anglefrom the outer peripheral edge of the annular flat portion 26 andprojecting upwardly in the axial direction by a predetermined heightdimension: H.

The tapered tubular portion 22 is formed with a tapered shape thatgradually increases in diameter going axially upward from the axialupper end of the shoulder portion 20. By means of the inner peripheralface of this tapered tubular portion 22, there is formed a tapered innerperipheral face 32 of funnel shape that gradually increases in diameterand opens out going axially upward from the upper edge of the tubularinner peripheral surface 30 of the shoulder portion 20. The flangeportion 24 integrally formed at the upper opening of the tapered tubularportion 22 is of annular plate shape having front and back surfaces thatextend in the axis-perpendicular direction, with a reinforcing rib 33that projects axially downward being formed at the outer peripheraledge.

Meanwhile, the male die 14 that, like the female die 12, is a moldedcomponent of synthetic resin, has an overall convex shape that projectsdownward, and generally has the shape of a body of rotation about thedie center axis 34. More specifically, the center portion of the maledie 14 is constituted as a spherical shell 36 that projects downward,with a tapered tubular portion 40 that extends upward integrally formedon the outer peripheral side of the spherical shell 36 via a shoulderportion 38, and with a flange portion 42 that spreads outwardly in theaxis-perpendicular direction integrally formed on the upper rim of thetapered tubular portion 40.

On the spherical shell 36, there is formed a convex forming face 44 thatcorresponds to the base curve of the target contact lens, this facebeing constituted by the surface on the convex side, which is the faceprojecting downward and facing in one axial direction (downward in FIG.1). The shoulder portion 38 extends in the circumferential directionwith a generally “L” shaped cross section that projects slightly outwardin the axis-perpendicular direction of the outer peripheral edge of thespherical shell 36 and then projects deflecting axially upward. As shownin FIG. 2, by means of the shoulder portion 38 there is formed a flatcontact face 46 as an annular flat face that extends outwardly in theaxis-perpendicular direction from the outer peripheral edge of theconvex forming face 44. This flat contact face 46 connects smoothly tothe outer peripheral edge of the convex forming face 44 so as to formthe lens edge, and is a flat face of annular shape extendingcontinuously around the entire circumference in the circumferentialdirection, spreading outwardly in the axis-perpendicular direction by aconstant width dimension: b (where b≦B). To the outer peripheral side ofthe flat contact face 46 is formed a sloped opposing face 48 that slopesupward in the axial direction and spreads out to the outer peripheralside.

In this embodiment in particular, the sloped opposing face 48 is formedextending continuously around the entire circumference with a crosssection that is bowed in an arcuate configuration that is downwardlyconvex in the axial direction. By so doing, in the forming mold forforming the male die 14, the surface for forming the sloped opposingface 48 can be machined easily and with high precision by means of acutting process using a turning tool. At the outer peripheral edge ofthe sloped opposing face 48 is an annular flat surface 49 having agentle slope angle over a predetermined width in the diametricaldirection and extending in the generally axis-perpendicular direction.

To the outer peripheral side of the sloped opposing face 48 in theshoulder portion 38 there is formed a vertical tubular outer peripheralsurface 50 that rises at an approximate right angle from the outerperipheral edge of the sloped opposing face 48 and projecting upwardlyin the axial direction by a predetermined height dimension: h. The sizeof the height dimension: h of the tubular outer peripheral surface 50 issuch that the sum (h+e) of h plus the rise dimension: e of the slopedopposing face 48 in the mating direction from the flat contact face 46is greater than the height dimension: H of the tubular inner peripheralsurface 30 of the female die 12.

The tapered tubular portion 40 is formed with a tapered shape thatgradually increases in diameter going axially upward from the axialupper end of the shoulder portion 38. The outer peripheral face of thetapered tubular portion 40 constitutes a tapered outer peripheral face52 that gradually increases in diameter and opens out axially upwardfrom the upper edge of the tubular outer peripheral surface 50 of theshoulder portion 38. A flange portion 42 integrally formed at the upperopening of the tapered tubular portion 40 is of annular plate shapehaving front and back surfaces that extend in the axis-perpendiculardirection, with a reinforcing rib 54 that projects axially upward beingformed at the outer peripheral edge.

In the female die 12 and male die 14 of the construction describedabove, the annular flat portion 26 of the female die 12 and the flatcontact face 46 of the male die 14 have substantially identical insidediameter dimension, whereas the outside diameter dimension of theannular flat portion 26 of the female die 12 is substantially identicalor slightly smaller than the outside diameter dimension of the slopedopposing face 48 of the male die 14. The tubular outer peripheralsurface 50 of the male die 14 has greater axial length than the tubularinner peripheral surface 30 of the female die 12, and the tapered outerperipheral face 52 of the male die 14 has a greater slope angle than thetapered inner peripheral face 32 of the female die 12. At the innerperipheral edge of the flange portion 42 a contact projection 56 thatprojects downward is integrally formed in annular configurationcontinuously in the circumferential direction, the bottom face of thiscontact projection 56 constituting a flat stopper face 58 that extendsout in the axis-perpendicular direction.

By so doing, by means of mating the female and male dies 12, 14 so thatthey are aligned in the axial direction on the die center axis 16, thetubular outer peripheral surface 50 of the shoulder portion 38 of themale die 14 is inserted and fitted in the axial direction against thetubular inner peripheral surface 30 of the shoulder portion 20 of thefemale die 12, until finally the flat contact face 46 of the shoulderportion 38 of the male die 14 abuts the annular flat portion 26 of theshoulder portion 20 of the female die 12, mutually positioning the two.That is, during mating, the female and male dies 12, 14 are mutuallypositioned in the axis-perpendicular direction by means of a tubularfitted portion 60 composed of the tubular inner peripheral surface 30and the tubular outer peripheral surface 50, as well as being positionedin the axial direction through abutment of the flat contact face 46against the annular flat portion 26, so as to be able to ensure propershape on the part of the forming cavity 15. Even in the event that theannular flat portion 26 or flat contact face 46 is deformed, since thestopper face 58 of the contact projection 56 formed on the flangeportion 42 of the male die 14 is placed in abutment with this flangeportion 24 of the female die 12, unnecessary proximity or relative tiltof the two female and male dies 12, 14 is avoided and proper shape ofthe forming cavity 15 is assured. As will be apparent from the precedingdescription, even with the female and male dies 12, 14 mated with theannular flat portion 26 and flat contact face 46 abutting each other,the stopper face 58 of the contact projection 56 in the male die 14 ispositioned in opposition, spaced slightly apart from the flange portion24 of the female die 12.

With the female and male dies 12, 14 mated in this state, in thesuperimposed regions of the shoulder portions 20, 38, the flat contactface 46 of the male die 14 is in intimate contact with the annular flatportion 26 of the female die 12, over an area of predetermined planardimensions extending in annular configuration continuously in thecircumferential direction by a predetermined width: b in theaxis-perpendicular direction. Coupled with the female and male dies 12,14 being held coaxially by the tubular fitted portion 60 in the mannerdescribed above, intimate contact between the annular flat portion 26 ofthe female die 12 and the flat contact face 46 of the male die 14 can beachieved stably and with high accuracy, whereby the forming cavity 15can be formed with a stable shape and sealed at the outer peripheraledge. As will be apparent from this, in this embodiment, the mutualcontact areas 62 are formed by means of the annular flat portion 26 ofthe female die 12 and the flat contact face 46 of the male die 14 whichare brought into abutment with each other during mating.

With the female and male dies 12, 14 in the mated state, the slopedopposing face 48 of the male die 14 is positioned in opposition to theannular flat portion 26 of the female die 12, spaced apart therefrom bya predetermined distance in the axial (mating) direction. By so doing,the annular auxiliary cavity 64 that extends continuously in thecircumferential direction is formed between the opposing faces of thesloped opposing face 48 of the male die 14 and the annular flat portion26 of the female die 12.

This auxiliary cavity 64 at the inside peripheral portion thereof issealed off by the mutual contact areas 62 of the female and male dies12, 14, and at the outside peripheral portion is substantially sealedoff by the tubular fitted portion 60 of the female and male dies 12, 14,so that the polymerizable monomer cannot readily leak out. That is, theforming cavity 15 is formed to the inner peripheral side, and theauxiliary cavity 64 to the outer peripheral side, with the mutualcontact areas 62 of the female and male dies 12, 14 situatedtherebetween, so that each is formed with a substantially sealedstructure.

In the female and male dies 12, 14 mated in the manner described above,at a location further to the outer peripheral side of the tubular fittedportion 60, the tapered inner peripheral face 32 of the female die 12and the tapered outer peripheral face 52 of the male die 14 arepositioned in opposition spaced apart from each other, whereby anannular monomer reservoir 65 that extends continuously in thecircumferential direction is formed with a hollow structure. Thismonomer reservoir 65 may communicate with the outer space through thesuperimposed faces of the flange portions 24, 42 of the female and maledies 12, 14.

When molding (polymerizing) the target contact lens using the contactlens forming die 10 composed of the female die 12 and male die 14described above, first, as shown in FIG. 3, the female die 12, which hasbeen produced by injection molding or the like, is supported on anappropriate jig so as to open upward in the vertical direction. In thesaucer-shaped area formed by the concave forming face 20 of thespherical shell 18, a polymerizable monomer 66 suitable for producingthe target ophthalmic lens is supplied by injection through an injectiontube 68. The amount of polymerizable monomer 66 supplied to the femaledie 12 is established so as to fill not only the forming cavity 15formed between the mating faces of the female die 12 and the male die14, but also the auxiliary cavity 64.

As the polymerizable monomer 66 it is possible to employ appropriatelyany of the various kinds of liquid monomer compositions known in the artfor use as starting materials for soft contact lenses and hard contactlenses; for example, besides any one or more of the radicalpolymerizable compounds commonly employed to date, materials could becomposed of macromers or prepolymers as well. Such compounds may takethe form of liquid monomer compositions that optionally includeappropriate crosslinking agents, polymerization initiators (e.g. thermalpolymerization initiators, photopolymerization initiators etc.),sensitizers, or other additives.

Then, as shown in FIG. 1 and FIG. 4, the male die 14 is superimposedagainst the female die 12 from above in the vertical direction, with thedie center axes 16, 16 aligned. This superimposition of the female andmale dies 12, 14 is accomplished with the outer peripheral face of theshoulder portion 38 of the male die 14 guided in the axial direction bythe tapered inner peripheral face 32 of the female die 12, while fittingthe tubular outer peripheral surface 50 of the male die 14 into thetubular inner peripheral surface 30 of the female die 12 and exertingmold closing load (mating force) of predetermined magnitude across thefemale die 12 and the male die 14 in the direction of the die centeraxis 16, to superimpose the convex forming face 44 of the male die 14against the concave forming face 22 of the female die 12.

Here, in preferred practice, mating will be carried out with one or bothof the female and male dies 12, 14 placed in a high temperature stateabove normal temperature, so that the female die 12 and/or male die 14is in a softened state. In this embodiment in particular, the male die14 is injection molded later than the female die 12, and duringinjection molding, the male die 14 is mated with the female die 12 afterthe male die 14 has been released from the mold for forming it (notshown), but before the forming resin material cools down completely toroom temperature from the high temperature state. The female die 12 mayalso be used before it has completely cooled down to room temperature.

By using the male die 14 in a high temperature state when mating it withthe female die 12, the male die 14, which is fabricated of thermoplasticresin material, may be reduced in hardness and made readily deformablefor mating of the male die 14 and the female die 12. Thus, during matingand subsequent clamping, the female and male dies 12, 14 can be securedfitting securely and in a substantially sealed state by means of thetubular fitting portion 60. It is also possible to make the female andmale dies 12, 14 conform in shape to each other at the mutual contactareas 62 so as to stably produce a highly sealed state.

As shown in FIG. 4, by means of mating the female and male dies 12, 14,the sealed forming cavity 15 and auxiliary cavity 64 filled with thepolymerizable monomer 66 are formed. Excess polymerizable monomer 66remaining after the forming cavity 15 and auxiliary cavity 64 are filledpools in the monomer reservoir 65, so as to avoid spilling out from theforming die 10. Next, with the female die 12 and the male die 14 held inthe mated state, polymerization of the polymerizable monomer 66 iscarried out. During the polymerization process, it is acceptable toexert a predetermined level of mating force across the female and maledies 12, 14.

While thermal polymerization or the like would be possible through theaddition of a thermal polymerization initiator to the polymerizablemonomer 66, in this embodiment, in order to avoid the effects of heat onthe female and male dies 12, 14 and on the polymerizable monomer 66, itis preferable to employ photopolymerization through irradiation withultraviolet, using a photopolymerization initiator. Where a monomerphotopolymerizable with ultraviolet radiation or the like is employed,the female and male dies 12, 14 will be formed of light-transmissivematerial.

During mating in the manner described above, by spreading out thepolymerizable monomer 66 dispensed onto the concave forming face 20 ofthe female die 12 as depicted in FIG. 3, by pushing the convex formingface 44 of the male die 14 against it from above, the monomer may beinduced to fill up the forming cavity 15; and by pushing and spreadingit further, may be led from the outer peripheral portion of the formingcavity 15 into the auxiliary cavity 64 and then made to fill theauxiliary cavity 64, becoming pushed out from the outer peripheralportion of the auxiliary cavity 64 into the monomer reservoir 65. Thesurface of the male die 14 which pushes and spreads out thepolymerizable monomer 66 from above is made up not only of the convexforming face 44 that forms the forming cavity 15, but also of thesmooth, bump-free surface including the flat contact face 46 formedcontinuously with the outer periphery thereof, and the sloped opposingface 48 in turn formed continuously with the outer periphery thereof. Asshown in FIG. 1 and FIG. 2, there are no inflection points along theentire length in the diametrical direction, the surface of each area isconnected smoothly by a common tangent. Additionally, in thisembodiment, the convex forming face 44, the flat contact face 46, andthe sloped opposing face 48 of the male die 14 are formed such that anypoint on their surfaces is situated uppermost in the axial direction(parting direction) when looking towards the inner peripheral side, andsituated lowermost in the axial direction (mating direction) whenlooking towards the outer peripheral side.

By means of pushing and spreading out the polymerizable monomer 66 withthe bottom face of the male die 14 which is smooth overall and whichprojects gradually downward towards the center from the outer peripheralside, the polymerizable monomer 66 may be pushed and spread outsmoothly, effectively avoiding residual air, as well as rapidly andstably filling the forming cavity 15 and the auxiliary cavity 64 withthe polymerizable monomer 66.

On the male die 14, the surface extending from the convex forming facethat forms the forming cavity 15, through the flat contact face 46 andup onto the sloped opposing face 48 extends smoothly in the diametricaldirection overall. With the sloped opposing face 48 consisting of abowed convex shape, and the auxiliary cavity 64 formed by the opposingfaces of the sloped opposing face 48 and the annular flat portion 26 ofthe female die 12 is situated between smoothly towards the innerperipheral side.

Thus, with the polymerizable monomer 66 in the initial stage ofpolymerization, and with the flat contact face 46 and the annular flatportion 26 not yet placed securely in intimate contact, negativepressure generated by polymerization shrinkage occurring aspolymerization proceeds from the generally center portion of the formingcavity 15 is advantageously reduced or eliminated by the replenishingaction of the polymerizable monomer which is led from the auxiliarycavity 64 along the 20 smooth sloped opposing face 48 towards the innerperipheral side and led into the forming cavity 15 through the slightgap between the flat contact face 46 and the annular flat portion 26. Bymeans of the negative pressure-mitigating action within the formingcavity 15 during the initial stage of polymerization molding, themolding defects such as residual stress or surface sink of thepolymerization-molded contact lens can be effectively avoided.

In this way, by means of polymerization of the polymerizable monomer 66in the forming cavity 15, there is formed a contact lens of the targetshape corresponding to the shape of the forming cavity 15. After thepolymerization process, the female and male dies 12, 14 are parted, andthe formed contact lens is released, completing manufacture of thetarget ophthalmic lens.

During the process of polymerization of the polymerizable monomer 66which fills the forming cavity 15, at generally the same time therewith,the polymerizable monomer filling the auxiliary cavity 64 is alsosubjected to the polymerization process. Where the polymerizable monomer66 is photopolymerizable, for example, this operation can be achievedreadily by simultaneous ultraviolet irradiation of the polymerizablemonomer 66 filling both the forming cavity 15 and the auxiliary cavity64. In order to specify which die the contact lens will remain attachedto when the female and male dies 12, 14 are parted, in preferredpractice, the cavity forming face of the female die 12, male die 14 orboth, i.e. the concave forming face 25 and/or the convex forming face44, will be subjected to high frequency glow discharge, coronadischarge, ultraviolet irradiation, atmospheric pressure plasma or otherknown process.

According to the ophthalmic lens manufacturing process described above,the female and male dies 12, 14, during mating thereof, are positionedfitted together with high accuracy on the same axis by the tubularfitted portion 60 superimposed accurately in a state of intimate contactwith each other at mutual contact areas 62 of established planardimensions or predetermined width. With this arrangement, the formingcavity 15 is defined with high accuracy, there is good cut-off of theresin material in the mating zone formed to the outer peripheral edge ofthe forming cavity, and the target contact lens can be manufactured withexcellent dimensional accuracy and stability. That is, in the mutualcontact areas 62 of the female and male dies 12, 14 at the outerperipheral edges of the forming cavity 15 where burrs or other moldingdefects of the contact lens tend to occur, not only is the area ofplanar contact of the female and male dies 12, 14 made larger, butrelative tilt of the female and male dies 12, 14 is prevented by thetubular fitted portion 60 so that a stable state of intimate contact isachieved. This makes it possible to seal the outer peripheral edge ofthe forming cavity 15 stably with high accuracy, as well as stablyobtain forming surface shape with high accuracy, so that the targetcontact lens can be produced with good accuracy while avoiding burrs andother defects.

In particular, in this embodiment, the female die 12 is composed of aflat annular flat face 26 that includes the mutual contact portion 62and whose face to the outer peripheral side thereof extends in theaxis-perpendicular direction overall. On the male die 14, the mutualcontact portion 62 is composed of the flat contact face 46 that extendsin the axis-perpendicular direction, with the outer peripheral edge ofthe flat contact face 46 connecting smoothly to the sloped opposing face48 of bowed convex shape that rises up smoothly. Accordingly, whenmolding the female die 12 and the male die 14 by means of injectionmolding or the like, it is possible to readily mold the annular flatface 26, the flat contact face. 46, and the sloped opposing face 48 withthe forming face of a single mold member, and since no inflection pointsare present on the forming face, it is possible to prevent theoccurrence of burrs at the contact faces of the female and male dies 12,14 forming the mutual contact areas 62 and the surrounding area. Thus,no special procedure for removing burrs after molding the female andmale dies 12, 14 is required, and when the female and male dies 12, 14are mated, it is possible to accurately and stably achieve intimatecontact in the mutual contact areas 62, in particular the innerperipheral edge thereof, so that the contact lens molded article can bemolded with higher accuracy and stability without molding defects suchas burrs.

If the width dimension: b of the mutual contact areas 62 of the femaleand male dies 12, 14 is too small it becomes difficult to ensure anadequate level of intimate contact, so in preferred practice b≧0.01 mm,more preferably b≧0.1 mm. If the width dimension: b of the mutualcontact areas 62 is too large, problems such as difficultly in ensuringa level of mold accuracy needed to maintain high precision of flatnessoverall, a large forming mold, and so on may result, so in preferredpractice b≦2.0 mm, more preferably b≦1.0 mm.

Additionally, in the contact lens forming die 10 having the constructiondescribed above, to either side of the mutual contact areas 62, theforming cavity 15 is situated to the inside in the circumferentialdirection and the auxiliary cavity 64 is situated to the outside in thecircumferential direction, with the polymerizable monomer 66 within thegenerally closed cavities 15, 64 being subjected to polymerizationgenerally at the same time, whereby tensile force created bypolymerization shrinkage of the polymerizable monomer 66 is exerted onthe inside faces of the two cavities 15, 64, and tensile force based onthe polymerization shrinkage can be efficiently directed onto the mutualcontact areas 62 of the female and male dies 12, 14, in a directionpushing the flat contact face 46 of the male die 14 towards the flatface 26 of the female die 12 in the mating direction.

In particular, acting force in the mating direction exerted on thefemale and male dies 12, 14 by means of polymerization shrinkage of thepolymerizable monomer 66 acts not only on the inner peripheral side ofthe mutual contact areas 62 but also on the outer peripheral side,whereby the occurrence of moment exerted on the mutual contact areas 62in a twisting or bending direction can be suppressed, with acting forcein the mating direction exerted on the female and male dies 12, 14 bymeans of polymerization shrinkage of the polymerizable monomer 66 beingmade to act efficiently as abutting force in the mating direction in themutual contact areas 62, whereby it is possible to bring the mutualcontact areas 62 into intimate contact stably with high accuracy todefine the target forming cavity 15, and thus to manufacture the targetcontact lens stably with high accuracy.

In order to exert force based on polymerization shrinkage of thepolymerizable monomer 66 in the forming cavity 15 and acting force basedon polymerization shrinkage of the polymerizable monomer 66 in theauxiliary cavity 64 to be advantageously exerted as abutting force inthe mating direction on the mutual contact areas 62, in preferredpractice, the capacity of the auxiliary cavity 64 will be 1% or more ofthe capacity of the forming cavity 15, and more preferably 10% or more.Since force exerted in the mating across the female and male dies 12, 14based on polymerization shrinkage of the polymerizable monomer 66 variesdepending on the projected area of the forming cavity 15 and theauxiliary cavity 64 in the mating direction, the projected area of theauxiliary cavity 64 projected in the mating direction onto a planeorthogonal to the die center axis 16 will preferably be 5% or more ofthe projected area of the forming cavity 15 similarly projected in themating direction, more preferably 10% or more. However, if the auxiliarycavity 64 is too large, there will be unnecessary consumption ofpolymerizable monomer 66 during molding of the contact lens, so inpreferred practice the capacity of the auxiliary cavity 64 will notexceed 250% of the capacity of the forming cavity 15.

In this embodiment in particular, when mating the female and male dies12, 14, by placing at least one of the dies in a high temperaturesoftened state, it is possible to more advantageously stably achieveintimate contact in the mutual contact areas 62, and thus to carry outmanufacture of the target contact lens stably with a higher level ofaccuracy. In order to ensure a higher level of dimensional and shapestability of the mutual contact areas 62, and hence the forming cavity15, and also of the contact lens, and to further improve productquality, when mating the female and male dies 12, 14, it is effective tobring only one them to a high temperature softened state so that thereis a certain difference in hardness between the two dies 12, 14, therebyavoiding irregular deformation of the two dies, and making it possibleto advantageously ensure the shape of the forming cavity 15 by means ofthe one hard die. As a specific example, where the female and male dies12, 14 are fabricated of polypropylene, mating will preferably becarried out the female die 12 at room temperature (20° C.), while themale die 14 is in a high temperature state of 30° C. or above,preferably 35° C. above.

As described above, by carrying out mating using the male die 14 in ahigh temperature state after having been molded of predetermined resinmaterial, there is no need to subsequently heat the male die 14,obviating the need for a special heating apparatus, as well as reducingheating time as compared to where subsequent heating is employed, sothat the contact lens molding cycle can be improved.

Additionally, in the forming die 10 having the construction describedabove, the female and male dies 12, 14 are secured together fitting bythe tubular fitted portion 60, so even if the die closing force isreleased or lowered after mating, the female and male dies 12, 14 can beheld stably in the mated state, and thus even when the mated dies aretransported to a polymerization apparatus or the like, it isnevertheless possible to effectively prevent molding defects resultingfrom a change in the mated state of the female and male dies 12, 14.

While the invention has been described hereinabove in terms of a certainpreferred embodiment, this is merely exemplary and is not intended to beconstrued as limiting the invention to the specific disclosure in theembodiment. Various alterations, modifications, and improvementsapparent to those skilled in the art may result in other embodimentswhich will nevertheless fall within the scope of the invention insofaras they do not depart from the spirit of the invention.

For example, the shape of the forming faces 25, 44 of the female andmale dies may be spherical or aspherical (e.g. elliptical), inconsideration of the shape of the target ophthalmic lens.

In the preceding embodiment, an annular flat surface 26 is formed on thefemale die 12, while a flat contact face 46 and a sloped opposing face48 of bowed cross section is formed on the male die 14. However, thesloped opposing face 48 could instead be configured as a tapered face oflinear cross section as shown in FIG. 5, or of notched shape as shown inFIG. 6. Alternatively, as depicted in FIG. 7, it would be possible, inthe reverse of the embodiment described hereinabove, to form the annularflat surface 26 on the male die 14, while forming the flat contact face46 and sloped opposing face 48 on the female die 12.

Further, whereas in the embodiment hereinabove, the tubular innerperipheral surface 30 of the female die 12 and the tubular outerperipheral surface 50 of the male die 14 in the tubular fitted portion60 fit together in a generally entirely tight state at theirdiametrically opposed faces that extend all the way around thecircumferential direction, so as to ensure a high degree of sealing ofthe auxiliary cavity 64 formed between the female and male dies 12, 14,according to the spirit of the present invention, the auxiliary cavity64 need only have sealed construction to the extent of preventing thepressure of the polymerizable monomer 66 from being completely releasedto atmospheric pressure during polymerization of the polymerizablemonomer 66. Thus, the polymerization shrinkage of the polymerizablemonomer 66 may be exerted on the female and male dies 12, 14 in themating direction. This is referred to as substantially sealedconstruction of the auxiliary cavity 64. Accordingly, it is possible toadjust the level of intimate contact in the tubular fitted portion 60 ofthe female and male dies 12, 14, in consideration of factors such asviscosity of the polymerizable monomer 66 employed, its change incharacteristics when polymerized, and localized differences in theextent to which polymerization proceeds when the polymerizable monomer66 is polymerized.

Specifically, for example, by forming a groove 72 extending in the axialdirection (mating direction of the female and male dies 12, 14) on thetubular inner peripheral surface 30 of the female die 12 as depicted inFIGS. 8-9, or forming a groove 74 extending in the axial direction onthe tubular outer peripheral surface 50 of the male die 14 as depictedin FIGS. 10-11, it is possible to form an outlet gap 76 by way of a gapthat extends through the tubular fitted portion 60 when the female andmale dies 12, 14 are mated, which gap is small enough that the negativepressure accompanying polymerization shrinkage during polymerization ofthe polymerizable monomer filling the auxiliary cavity 64 does notescape. That is, by forming an outlet gap 76, in the stage prior topolymerization of the polymerizable monomer it is possible for excesspolymerizable monomer 66 filling the forming cavity 15 and the auxiliarycavity 64 to be expelled to the outside through the outlet gap 76 duringmating of the female and male dies 12, 14. Thus, even where the femaleand male dies 12, 14 are mated by being press-fit under high pressurefor example, elevated fill pressure of the polymerizable monomer 66 inthe forming cavity 64 can be reduced or avoided and lift (slightparting) of the female and male dies 12, 14 after mating due to residualfill pressure can be prevented, thereby making possible a higher levelof accuracy in molding, as well as avoiding a condition of initial highpressure in the auxiliary cavity 64 prior to polymerization, so as tomore effectively exhibit the target fitting assist force on the femaleand male dies 12, 14 that accompanies polymerization shrinkage of thepolymerizable monomer 66.

By appropriately setting the characteristics of the polymerizablemonomer 66 used, the polymerization procedure, and the like, the outletgap 76 for expelling excess polymerizable monomer 66 from the auxiliarycavity 64 during mating of the female and male dies 12, 14 can beestablished in appropriate size, number and location, within a rangesuch that negative pressure created in the auxiliary cavity 64 on thebasis of polymerization shrinkage is not prevented from beingeffectively exerted on the female and male dies 12, 14 as force in themating direction. Specifically, it is possible to form a plurality ofsuch outlet gaps 76 by means of forming a plurality of grooves 72 spacedapart in the circumferential direction on the tubular inner peripheralsurface 30 of the female die 12 as depicted in FIGS. 12-13, or forming aplurality of grooves 74 spaced apart in the circumferential direction onthe tubular outer peripheral surface 50 of the male die 14 as depictedin FIGS. 14-15.

In FIGS. 5-15 hereinabove, in order to aid understanding, parts andregions of similar construction to those of the embodiment are eachassigned the same symbol as in the embodiment in the drawings.

1. A contact lens forming die comprising a female die having a concaveforming face and a male die having a convex forming face, which aremated with each other to create a forming cavity between the opposedconcave forming face and convex forming face, the forming cavity adaptedto be filled with polymerizable monomer which is polymerized to form acontact lens, the contact lens forming die characterized in that, bymeans of mating the female die and the male die with each other, annularflat mutual contact areas extending over a width of 0.01 mm or greaterin a direction orthogonal to the die mating direction are formed byabutting the female and male dies at an outer peripheral side of theconcave forming face and the convex forming face, at an outer peripheralside of the mutual contact areas an auxiliary cavity of substantiallyclosed structure to be filled with the polymerizable monomer duringmolding is formed by the female and male dies positioned spaced apart inopposition to each other in a die mating direction; and a tubular fittedpart is formed by fitting together of the female and male dies at anouter peripheral side of the auxiliary cavity by means of tubularsurfaces extending in the die mating direction.
 2. A contact lensforming die according to claim 1, wherein a capacity of the auxiliarycavity is 1-250% of a capacity of the forming cavity.
 3. A contact lensforming die according to claim 1, wherein by means of mating the femaledie and the male die with each other, the male and female dies arepositioned spaced apart from each other by an outer peripheral side ofthe tubular fitted portion, forming an annular monomer reservoir thatcontains an excess polymerizable monomer during molding.
 4. A contactlens forming die according to claim 1, wherein in the female die, a faceforming the auxiliary cavity is a smooth surface devoid of bumps in anentirety thereof.
 5. A contact lens forming die according to claim 1,wherein the female die is formed with an annular flat surface extendingin a direction generally orthogonal to the die mating direction towardsan outer peripheral side from an peripheral edge portion of the concaveforming face, the annular flat surface of the female die being broughtinto abutment at an inner peripheral portion thereof with the male dieso as to form the mutual contact areas, and being positioned at an outerperipheral portion thereof in opposition to the male die spaced aparttherefrom in the die mating direction so as to form the auxiliarycavity.
 6. A contact lens forming die according to claim 5, wherein themale die is formed with an annular flat surface extending in a directiongenerally orthogonal to the die mating direction towards an outerperipheral side from an peripheral edge portion of the convex formingface, the annular flat surface of the male diem being brought intoabutment with the annular flat surface of the female die so as to formthe mutual contact areas, and a sloping face that extends towards theouter peripheral side from an peripheral edge portion of the annularflat surface of the male die and that moving towards the outerperipheral side becomes gradually further apart in the die matingdirection from the annular flat surface of the female die, the slopingface being positioned in opposition to the annular flat surface of thefemale die so as to form the auxiliary cavity, and having a tapered facethat slopes at a predetermined angle in the die mating direction andextends linearly towards the outer peripheral side, or a bowed convexface that projects out to the auxiliary cavity side and extends towardsthe outer peripheral side.
 7. A contact lens forming die according toclaim 1, wherein the tubular surface making up the tubular fittingportion in the female die is formed projecting from a peripheral edgeside of an auxiliary cavity forming face in the die mating direction ofthe female die with the male die.
 8. A contact lens forming dieaccording to claim 1, wherein a gap for expelling excess polymerizablemonomer in the auxiliary cavity to an outside during mating of the maleand female dies is formed in the tubular fitting portion.
 9. A methodfor manufacturing a contact lens characterized in that whenmanufacturing a contact lens using the contact lens forming diepertaining to claim 1, characterized in that with the forming cavity andthe auxiliary cavity formed between the mating faces of the female dieand the male die being filled with the polymerizable monomer, thepolymerizable monomer filling the forming cavity and the auxiliarycavity is subjected to a polymerization process.
 10. A method formanufacturing a contact lens according to claim 9, wherein the matingdirection of the male and female dies is generally vertical, with themale die being mated relative to the female die from above in thevertical direction.
 11. A method for manufacturing a contact lensaccording to claim 9, wherein at least one die selected from the maledie and the female die is a forming die of synthetic resin, and with themale and/or female die of synthetic resin in a softened state at hightemperature, the polymerizable monomer is supplied between the opposedface of the male and female dies, while mating the male and female diesso that the forming cavity and the auxiliary cavity are filled with thepolymerizable monomer.
 12. A method for manufacturing a contact lensaccording to claim 11 wherein at least one die selected from the maledie and the female die is a forming die of synthetic resin, with themale and/or female die of synthetic resin being mated used in a hightemperature state prior to completely cooling after molding thereof.